Uninstall and reinstall Opera like this.
While Opera is closed, in both "C:\Users\yourusername\AppData\Roaming" and "C:\Users\yourusername\AppData\Local", right-click on the "Opera Software" folder, click "properties", switch to the "General" tab, click the "read only" checkbox so that it's clear (all white) and click "apply". Then, switch to the "Security" tab, make sure your username is listed and make sure it has full control (all permissions set to allow). Don't worry about "special permissions".